Discussion of the suspension of a vehicle refers to the system of springs, shock absorbers and linkages that connects a vehicle to its wheels. Vehicle suspension systems serve a dual purpose—(1) contributing to the road holding/handling and braking of the vehicle for safety and driving pleasure, and (2) keeping vehicle occupants comfortable and reasonably isolated from road noise, bumps, vibrations, and the like. These two goals are generally at odds, so the tuning of suspensions involves finding the right compromise for each vehicle.
On the one hand, it is important for the suspension to keep the road wheels in contact with the road surface as much as possible, because all the forces acting on the vehicle do so through the contact patches of the tires. On the other hand, the suspension is intended to dissipate the translation of noise, ruts, bumps, vibration, and the like to protect the vehicle itself, and any cargo or luggage, from damage and wear. Often the designs used for the front and rear suspension of a vehicle, as well as any trailer in tow, are different.
Watt's linkage is one type of suspension used in the rear axle of some vehicles as an improvement over the Panhard rod, which was designed in the early twentieth century. Both methods intend to prevent relative sideways motion between the axle and body of the vehicle. Watt's linkage approximates a vertical straight line motion more closely, and does so while fixing the location of the center of the axle rather than toward one side of the vehicle, as more commonly used when fitting a long Panhard rod.
As shown in FIG. 1, Watt's linkage consists of two horizontal bars of equal length mounted at each side of the chassis. Between these two bars, a short vertical bar is connected. The center of this short vertical bar—the point which is constrained in a nearly straight line motion—is typically mounted to the center of the axle. All pivoting points are free to rotate in a vertical plane.
In a way, Watt's linkage can be seen as two Panhard rods mounted opposite each other. In Watt's arrangement, however, the opposing curved movements introduced by the pivoting Panhard rods are compensated by the short vertical rotating bar.
The problem is that these devices do not allow for corresponding adjustments due to changes in the vehicle center of gravity (Cg) height, load height, or other important variables. Current devices also do not allow for a roll center that is significantly higher than the frame rails of the vehicle. Finally, current designs do not facilitate using the transverse locating device for testing the effects of changing roll center to Cg induced moments. Rather, current devices require the driver to use a great deal of their attention to determine the appropriate cornering speed. This generally results in a greatly reduced speed and therefore increases transportation costs. A great deal of expensive time is required to change out all the suspension components required for installing the current types of devices used to determine differing roll center heights.
The present device solves these and other problems associated with current vehicle suspension systems.